Micro-climate cooling garments are known for maintaining workers in high temperature environments at a temperature below the environmental temperature in order to enable the worker to operate within the environment for an extended period of time in order to accomplish a desired task.
One such micro-climate cooling garment is disclosed in U.S. Pat. No. 4,856,294 to Scaringe et al. which discloses a micro-climate cooling system in the form of a self-contained vest comprising a vest-type garment having an interior cross-section of a double wall construction. The portion of the vest that is proximate the body is selected so as to be compatible with the skin of the wearer and the internal portion which forms a sealable pocket which contains a heat exchange or thermal energy transfer material that changes phase from a solid to a liquid within a range of body temperatures. While somewhat effective in accomplishing its intended purpose of cooling the wearer, the Scaringe et al. garment is not without its inherent drawbacks and disadvantages. For example, the Scaringe et al. vest is a solid stiff vest, covering generally the entire torso of the wearer. As a result, the wearer tends to sweat profusely while wearing the vest and perspiration cannot escape through the garment. This can result in an increase in the weight of the user, as the perspiration will most likely be captured by the garment or by the clothing of the wearer. In addition, the failure of the garment to breathe, can result in the wearer developing hypothermia. Furthermore, the Scaringe et al. vest completely ignores the fact that almost seventy five per cent of resting metabolic heat production is eliminated by convection and radiation and that sweating and evaporation are therefore the keys to heat rejection at higher levels of heating. The Scaringe et al. garment also fails to take into account that discomfort occurs when the area of the sweat-moistened body approaches forty per cent and that to transfer sufficient heat for comfort, a 1-4 degree centigrade thermal gradient is necessary between the deep core body temperature and the surface skin temperature. For deep core temperatures higher than 39 degrees centigrade and corresponding skin temperatures above 36 degrees centigrade, the risk of heat exhaustion increases. For the foregoing reasons the Scaringe et al. vest is not preferred, nor currently used by the military.
Another micro-climate cooling garment in the form of a vest is the so-called "Steele" vest which is specifically designed for military applications. The Steele vest is a one-piece design that can be slipped over the head of the wearer. Hook and loop side straps cinch the garment to improve contact with the body. Normally, the undergarment is worn over a T-shirt, but it may be worn over a military uniform in a NBC (nuclear, biological, chemical) protective suit. The Steele vest has six pockets (three over the front chest and another three across the back). Each pocket can hold a segmented three-element thermostrip of the blue gel PCM (phase change material) to facilitate fit to the human torso. The blue PCM employed in the Steele vest is a thin mixture of cornstarch and water. A sample of the Steele PCM was placed in a super-cold freezer and it was observed that the temperature of the PCM had to be lowered to below -20 degrees centigrade in order to freeze it. The PCM in the Steele vest melts over a range of -5 degrees centigrade to approximately 8 degrees centigrade. During testing it was noted by the inventor that the PCM packets had to be insulated from contact with the body to prevent frostbite and discomfort, factors which are believed to reduce the garment's effectiveness. Another disadvantage of the Steele vest is that the PCM, once melted must be re-frozen or re-solidified at approximately -25 degrees centigrade in order to remove the 55 cal/gram of latent energy stored before re-solidification. Thus, freezing the Steele PCM mixture to -15 degrees centigrade would not significantly rejuvenate it. In view of the foregoing, it would be commercially valuable to be able to provide a PCM that could be placed in direct or near direct contact with the skin in order to obtain maximum cooling power from the PCM. In addition, it would be a significant improvement over the prior art to provide a PCM that could be easily rejuvenated in the field without any special apparatus.
It is accordingly an object of the present invention to provide a micro-climate cooling garment that overcomes the above noted problems associated with the prior art devices, and which is comfortable.
More particularly, it is an object to provide a micro-climate cooling garment in the form of a vest that may be brought into direct or close contact with the skin of the wearer without causing frostbite or discomfort.
Another object of the present invention is to provide a microclimate cooling garment in the form of a vest that allows escape of perspiration from beneath the garment.
Yet another object of the present invention is to provide a micro-climate cooling garment in the form of a vest that may be recharged without any special apparatus.
Still another object of the present invention is to provide a micro-climate cooling garment in the form of a vest that provides freedom of movement to the wearer while closely conforming to the body shape of the wearer to provide maximum heat transfer between the vest and the wearer.
A still further object of the present invention is to provide a micro-climate cooling garment in the form of a vest that maintains a relatively uniform distribution of the phase change material while in the liquid state.